1. Field of the Invention
The invention relates to liquid crystal display panels, and more particularly relates to a method of driving a pixel and a liquid crystal display panel implementing the method.
2. Description of the Related Art
Conventional liquid crystal display panels employ a scanning frequency of about 60 Hz. Although a scanning frequency of 60 Hz is largely adequate, it is too slow for dynamic images and often results in image smear. To prevent image smear, one solution for preventing image smear is to increase the scanning frequency, for example, 120 Hz.
In a 120 Hz monitor, a frame displayed in a 60 Hz monitor is processed and divided into two sub-frames. For a pixel, the sum of the generated brightness in the two sub-frames is equal to the brightness generated in the original frame, but in another embodiment, the two sub-frames may have different brightness.
Although the increased scanning frequency can reduce image smear in dynamic images, it also reduces the charge/discharge period, and the voltage level of the pixel may not be capable of achieving the required data voltage. FIGS. 1A and 1B show voltage waveforms of a pixel of a 60 Hz monitor being charged, and voltage waveforms of a pixel of a 120 Hz monitor being charged. Vcom represents the voltage level of a common electrode. Pixels are enabled/disabled by their corresponding gate voltages Vgate. When a pixel is enabled by its gate voltage Vgate, a data voltage Vdata begins charging the pixel. Pixel voltage Vpixel represents the voltage level of the pixel. Referring to FIG. 1A, after the gate voltage Vgate enables the pixel, the pixel voltage Vpixel begins charging to the data voltage Vdata. At the end of time period T, the pixel voltage Vpixel achieves the data voltage Vdata. Referring to FIG. 1B, the amount of time for charging is T/2, half of that for conventional 60 Hz monitors, and is thus too short to charge the pixel voltage Vpixel to the data voltage Vdata. As shown in FIG. 1B, at the end of charging period, there is a voltage difference ΔVd-p between the pixel voltage Vpixel and the data voltage Vdata. The voltage difference ΔVd-p damages the image contact of the liquid crystal display panel. Thus, novel methods for driving a pixel capable of overcoming the described shortcomings are desirable.